Field of the Invention
The present invention relates to a photoacoustic microscope apparatus.
Description of the Related Art
Photoacoustic waves are a type of elastic waves that are generated in a thermoelastic process which occurs when light of an absorption wavelength range is irradiated to a substance. Therefore, the photoacoustic waves have been attracting attention as a technology for imaging absorption characteristics. Moreover, since the photoacoustic waves are a type of ultrasonic sound waves having characteristics that are not susceptible to be affected by scattering as compared to light, they have been used as a means for imaging inside of an organism.
In an photoacoustic microscope to be used for imaging the photoacoustic wave as a detection signal, a method in which, by using pulse light adapted to the absorption wavelength range of an object to be observed as excitation light, an inside of a specimen is scanned by a focused spot by focusing the excitation light by an objective lens, and the photoacoustic wave generated at positions of the focused spots are detected by a device such as a transducer, has been used. According to the photoacoustic microscope, when the specimen is scanned by the focused spot, since the photoacoustic waves are generated if there is an absorbing substance at the position of the focused spot, it is possible to carry out imaging of absorption characteristics in the specimen by detecting the photoacoustic wave.
As a photoacoustic microscope of such type, a photoacoustic microscope disclosed in Japanese Translation of PCT International Application Publication No. 2011-519281 has been known. FIG. 12 is a diagram showing the photoacoustic microscope disclosed in Japanese Translation of PCT International Application Publication No. 2011-519281. In FIG. 12, excitation light L from a laser pulse light source is focused to an inside of a specimen via a condenser lens 11, a pinhole 12, a vibrating mirror 13, an objective lens 14, a correcting lens 15, an isosceles prism 16, a silicone oil layer 17, a rhombic prism 18, and a photoacoustic lens 19. Moreover, photoacoustic wave U generated from focused positions inside a specimen S are gathered by the photoacoustic lens 19 and are subjected to wave-front conversion, and upon being reflected inside the rhombic prism 18, are detected by an ultrasonic transducer 20.
In FIG. 12, the isosceles prism 16 and the rhombic prism 18 are coupled via the silicone oil layer 17. The photoacoustic lens 19 is cemented to the rhombic prism 18 such that, a sound axis of the photoacoustic lens 19, which corresponds to an optical axis of an optical lens, coincides with an optical axis of the objective lens 14, and a focal position of the photoacoustic lens 19 coincides with a focal position of the objective lens 14. The ultrasonic transducer 20 is joined to the rhombic prism 18 such that, a wave-front of the photoacoustic wave U from a focal point of the photoacoustic lens 19 is converted to a plane wave by the photoacoustic lens 19, and is incident perpendicularly on a detection surface of the ultrasonic transducer 20. Moreover, the specimen S is immersed in a liquid.